In the control of drive units of motor vehicles, the reduction of the torque is delayed when there is a rapid withdrawal of the accelerator pedal by the driver in order to improve comfort (the so-called dashpot functions or load-impact damping functions). In this way, a damping of the otherwise occurring jolt is achieved. However, it is to be noted that an rpm overshoot is triggered which reduces driving comfort when there is a withdrawal of the accelerator pedal with a simultaneous pressing of the clutch pedal when the dashpot function is active. A solution for improvement would be to switch off this load-impact damping function when the clutch is actuated. However, for this purpose, the actuation of the clutch pedal has to be detected, for example, by means of switches or algorithms. A procedure of this kind is described, for example, in German patent publication 198 27 585. On the other hand, the use of clutch switches or of algorithms to detect the clutch actuation can be associated with problems with respect to the required accuracy. If, for example, a clutch switch is adjusted inaccurately, then, even though the clutch is depressed but the drive train not separated, the dashpot function does not operate so that a noticeable jolt can occur. If no clutch actuation is detected notwithstanding a separated drive train, then this leads to the overshoots which likewise negatively affect driving comfort.
An rpm overshoot is effectively prevented by the activation of an rpm limiter when withdrawing the accelerator pedal. This is done without detecting an actuation of the clutch pedal and/or a separation in the drive train. In this way, an rpm overshoot when disengaging the clutch is prevented during or after withdrawing the accelerator pedal under all conditions, also without clutch switches.
A jolt is effectively prevented by the continuous withdrawal of the rpm limiting intervention signal (torque reduction) when depressing the accelerator pedal after a deceleration already in advance of dropping the rpm via the limiting intervention.
The method of the invention is for controlling a motor of a vehicle and includes: determining the rpm of the motor and a quantity representing a command of the driver of the vehicle; determining a reference rpm of the motor at the start of a withdrawal of the command by the driver; and, limiting the rpm of the motor to the reference rpm when the driver withdraws the command.
Clutch switches or algorithms for detecting the clutch pedal actuation can be omitted without limiting comfort or limiting function.
Furthermore, a slight reduction of consumption and emission results via the immediate charge reduction for rpm overshoots because, in this case, the dashpot termination does not become effective, as well as via an immediately triggered overrun cutoff without further delay time as soon as the overrun state is detected.
The shift operation and the shift comfort are considerably improved overall by the introduction of the rpm limiter.